Spectral frequency and the modulation of the acoustic startle reflex by background noise.
The rat's (Long-Evans) acoustic startle reflex to a high-frequency tone burst (10.5 kHz) was depressed by intense high-frequency band-pass noise (8-16 kHz) but enhanced by low frequency noise (1-2 kHz). However, contrary to the hypothesis that the depression of startle in intense background noise is produced by sensory masking, the reflex to a low-frequency tone burst (at 1 kHz) was depressed by both high- and low-frequency band-pass noise. Two additional hypotheses are offered to supplement sensory masking in order to explain the asymmetry in these data. The first is that the intratympanic reflex, which acts as a high pass filter on acoustic input, is elicited in intense backgrounds. The second is that acoustic startle reflexes elicited by intense low-frequency tones are in part elicited by their high-frequency distortion products and that these distortion products are then masked by high-frequency background noise.
Gerrard
R L
RL
Department of Psychology, University of Rochester, New York 14627.
Ison
J R
JR
D000818:Animals; D001143:Arousal; D001288:Attention; D008144:Loudness Perception; D008297:Male; D009622:Noise; D010470:Perceptual Masking; D010898:Pitch Perception; D051381:Rats; D013216:Reflex, Startle; D013018:Sound Spectrography